1. Field of the Invention:
This invention relates to a process for preparing a powder of an alloy of a rare earth element, iron and boron which is used for making a resin bonded magnet.
2. Description of the Prior Art:
A magnet material composed of a rare earth element, iron and boron is known. A typical example is an alloy of neodymium (Nd), iron and boron. This class of material has drawn attention, since it has better magnetic properties and is less expensive than another type of magnet material that is composed of samarium (Sm) and cobalt (Co). The powder of an alloy of a rare earth element, iron and boron which is used for making a magnet is prepared by the melting process or the reduction and diffusion process.
According to the melting process, the starting materials, e.g., pure iron, an alloy of iron and boron and a rare earth metal, are melted, the melt is cast to form an ingot, the ingot is crushed into coarse particles, and the coarse particles are pulverized.
The reduction and diffusion process is started by mixing a powder of a rare earth oxide or a powder of a rare earth oxide and a rare earth metal, a powder containing iron, a powder containing boron, and at least one of an alkali metal, an alkaline earth metal and a hydrogenated product thereof. The mixture is heated at a temperature of 900.degree. C. to 1200.degree. C. in a non-oxidizing atmosphere, e.g., in an inert gas atmosphere or in a vacuum. The resulting reaction mixture containing CaO and residual calcium is subjected to wet treatment.
Both of the processes are, however, deficient. The materials which the melting process employs are expensive and more than one step of crushing is required. The reduction and diffusion process can produce only an alloy powder of low magnetic properties.